AJP - Heart and Circulatory Physiology, Vol 244, Issue 1 109-H114, Copyright © 1983 by American Physiological Society
Maximum fluid concentrations of materials released from platelets at a surface
G. A. Adams and I. A. Feuerstein
We examine the estimation of local concentrations of materials that are
released from the dense and alpha-granules of platelets during accumulation
of platelets upon collagen-coated glass. Platelet/red blood cell
suspensions were perfused through a 1.3-mm-ID tube. Empirical data were
used in a calculation procedure, based on diffusion and convection,
designed to yield an upper bound on the interfacial fluid concentration
(IFC) for each substance considered. The necessary empirical data are the
rate of platelet accumulation and the maximum amount of material in the
platelet capable of secretion. It was found that the IFC is dependent on
the shear rate at the surface (G) and is proportional to G0.27. This means
that an eightfold increase in flow rate would increase the IFCs
approximately twofold. Serotonin, pyrophosphate, adenosine 5'-monophosphate
(AMP), and adenosine 5'-triphosphate (ATP) were found not to be present in
sufficient quantities to produce IFCs that could influence platelet
aggregation if used alone at the IFC. A second set of materials,
fibrinogen, fibronectin von Willebrand factor, and calcium, had IFCs less
than their concentrations normally found in plasma. A third category,
containing adenosine 5'-diphosphate (ADP) alone, had an IFC close to those
known to affect platelet aggregation. The role of metabolites of
arachidonic acid, which may promote or inhibit platelet aggregation, awaits
further description.
